Bar screens or grids are conventionally utilized in the removal of trash or debris from waste liquid, such as sewage, either in a channel or the like or as the liquid flows into a well or sump, in which it is collected for feeding to a lift pump which elevates the liquid to a higher elevation for flow to another collection system or to a treatment plant or the like. In a channel, a bar screen necessarily extends from side to side of the channel, while previous bar screens, at the mouth of a pipe which conveys the liquid into a sump or well for the above purposes, also extends from side to side or wall to wall of the well or sump. Such bar screens are subject to plugging, i.e. trash or debris collecting thereon, if not removed, for example, if a mechanical or electrical failure should occur, may stop the flow through the channel, pipe or the like. This plugging may result in sewage overflowing manholes in the streets, backing up into building and home basements, causing sedimentation and consequent blockage in the sewer pipes, or the like. Also, such bar screens have been cleaned by front or rear grids or rakes, normally moved downwardly in spaced relation to a fixed screen or grid, but when a position opposite the lower end of the screen or grid is reached, moved forwardly until the cleaning grid or rack is inserted under the debris or trash collected by the bar screen, then moved upwardly along the bar screen. After reaching the top of the bar screen, the cleaning grid or rack is elevated to a position in which it may deposit the collected debris or trash, as into a receptacle or other suitable place. Normally, a bar screen or rake slants upwardly from the bottom of a tunnel and the movement of the cleaning grid or rake along the bar screen corresponds to such inclination. Bar screens or grids which are cleaned from the front may extend to the top of a channel or the like. However, upright bar screens or grids which are cleaned from the rear require that the generally horizontal teeth, bars or the like of the cleaning rake be inserted between the generally upright bars of the grid or screen to be cleaned, then moved upwardly past the upper ends of the fixed grid or rack, which must be free for passage of bars or teeth of the cleaning rake. Irrespective of whether a fixed screen or grid is cleaned from the front or rear, the extension thereof to the wall at each side, whether in a channel or in a well or sump, again presents the possibility of plugging. Cleaning devices which include a rake moved downwardly in front to the lower end of a fixed grid or screen, then moved toward the grid or screen and then upwardly, may be represented by the pivoted rake of U.S. Pat. No. 3,358,837 or a rake which moves around a loop track, as of U.S. Pat. Nos. 2,128,347 or 3,591,006. There are also similar devices for cleaning from the reverse or rear side of the grid.
There are also variations, as in U.S. Pat. Nos. 3,836,463 and 3,856,216, which utilize a disintegrating device disposed between a pair of laterally spaced, upwardly inclined bar screens, through which the liquid flows but on which the trash or debris is caught, then moved upwardly by rakes which are reciprocated along the bar screens from the base to the upper end of each, then away from the screen and downwardly to the starting position. In the magazine PUBLIC WORKS for April 1982, at pages 66-68, a sewage lift station is disclosed having a basket strainer covering the end of a pipe discharging into a well, from which the liquid is fed to an elevating pump, and, in a modified system, a flat stock bar screen which surrounds the discharge end of a pipe, is utilized for a similar purpose. Although the actual improvement described in this article is in the pump installation, each of these screens illustrates an extension to each side of an outlet and to a wall. Also, both the basket strainer and the flat stock bar screen were cleaned manually by access through a manhole cover directly above. Nevertheless, the possibility of such a strainer or screen becoming plugged is evident.
Among the objects of this invention are to provide a bar screen which will intercept trash or debris carried by a liquid without becoming plugged; to provide such a bar screen which is open at the sides, or other appropriate position; to provide such a bar screen which may be periodically lifted in order to discharge the collected trash or debris into a receptacle or the like; to provide such a bar screen which is particularly adapted to collect trash or debris flowing through a pipe which discharges into a well or sump at a lift station; to provide such a bar screen which may be periodically moved upwardly to a dumping position but is utilized in conjunction with a screen gate which may automatically cover the mouth of the pipe while the collection screen is being dumped; to provide such a bar screen which is particularly adapted to be placed in a fixed position at the discharge end of a pipe or the like but which is open at the sides or other appropriate position to prevent blocking of liquid flow; to provide each such type of bar screen which is readily constructed, which is generally low in cost and which is effective in operation; to provide a rake especially adapted to remove the collected trash or debris from such a fixed bar screen; to provide such a rake which has fingers or the like which may be moved upwardly between the bars of the fixed bar screen; to provide such a rake which may be automatically unloaded at an upper position; and to provide such rakes which are readily constructed, generally low in cost and effective in operation.